Process for inlaying poured metal in wood

ABSTRACT

A process for inlaying by pouring molten metal directly into a wood cavity without visibly charring or burning the outer wood surface. The process consisting essentially of the steps of routing out the desired design in a wood surface, providing a heat resistant and heat absorbent material in contact with the wood surface adjacent the design, pouring a liquid metal into the design formed in the wood so that metal fills the design to an elevation slightly above the final surface, removing the heat resistant and heat absorbent material, and sanding the wood surface and the raised metal until both metal and wood are at the same elevation.

ilnite States atent 1191 Mitchell 1451 Oct. 22, 1974 1 PROCESS FOR INLAYING POURED METAL 1N WOOD [76] Inventor: Byron V. Mitchell, 17554 Meekland Ave, Hayward, Calif. 94541 [221 Filed: July 2, 1973 [21] Appl. No.: 375,895

1948, pp. 7043. Silicones Ease Many Production Tasks," Plastics World, Oct. 1963, pp. l4l5.

Primary Examiner-Charlcs W. Lanham Assistant Examiner-D. C. Reiley, lll Attorney, Agent, or Firm-James R. Cypher [57 1 ABSTRACT A process for inlaying by pouring molten metal directly into a wood cavity without visibly charring or burning the outer wood surface. The process consisting essentially of the steps of routing out the desired design in a wood surface, providing a heat resistant and heat absorbent material in contact with the wood surface adjacent the design, pouring a liquid metal References Cited into the design formed in the wood so that metal fills UNITED STATES PATENTS the design to an elevation slightly above the final sur- 1157456 W939 Kuyemunnm 29/5272 UX face, removing the heat resistant and heat absorbent 3,322,184 5/1967 Cofcr m1 164/72 material. and Sanding the Wood surface and the raised 3.671.007 6/1972 Bailey et a1. ll7/5.1 X metal until both metal and wood are at the same el'c OTHER PUBLICATIONS K. Rose, Lightness and Strength Combined in 11 Claims, 14 Drawing Figures Metal-Wood Composite, Materials & Methods, Feb.

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sum NF 2 HOT METAL PROCESS FOR INLAYING POURED METAL IN WOOD BACKGROUND OF THE INVENTION Since the earliest times when man learned to produce metal from their ores and cast the metals into various shapes, he has tried to combine metal and wood into a single object. Since metal melts at a'very high temperature, all attempts to cast metal directly into wood resulted in the destruction of the wood by burning or charring. Skilled artisans became proficient therefore in casting a metal design in sand or metal molds care fully carving out the exact shape of the design in the wood and then mechanically setting the metal design into the prepared cavity in the wood. The steps of casting the metal separately and inlaying it into the wood is both costly and time consuming. The result is that very few wood pieces are constructed with metal inlays.

Imperfect results were obtained by applicant by protecting the wood surface with asbestos paper but it was extremely difficult to trim the paper exactly to the design routed into the wood. Further, the paper tended to char at the edges of the design and after one or two uses, the paper had to be replaced. Thus it was impossible to obtain any degree of mass production of poured metal inlays in wood.

SUMMARY OF THE INVENTION tively new material originally produced to coat the heat shields on space vehicles to prevent the destruction of the metal upon re-entry into the earths atmosphere. This material is known commonly as RTV (room temperature vulcanizable); is produced by General Electric and Dow Chemical Company and is used to a limited extent in making molds for casting objects in the usual manner in which the metal is removed from the mold when the metal has solidified. The RTV material in the present invention is used in a new manner with new andsurprising results. The RTV material is placed next to the wood surface adjacent to the routed out portion of the wood rather than in the cavity and surprisingly prevents the wood from becoming charred or burned while the molten metal is poured into the design previously made in the wood.

An object of the present invention is to provide a process by which molten metal con be poured directly into a cavity in a wood surface with the 600 to 700F molten metal coming directly into contact with the uncoated wood to form a metal inlay design form member.

Another object is to produce metal inlays in wood on a relatively inexpensive mass production basis.

A further object is to produce metal inlays in wood in such objects as wood servingtrays, ice buckets, meat carving blocks, table hot pads, furniture, wood plaques, in situ paneling, wood bowls, winebottle holders and other decorative and useful objects.

A further objective is to provide metal inlays in wood of a design complexity and beauty never before achieved.

A still further objective is to provide a metal inlay in wood in which it is impossible to remove the inlay without destruction of the wood and it is impossible to see by what means the metal is attached to wood.

Another object is to produce metal inlays in wood by the process described so that there is no char or burn marks in the wood visible to the naked eye.

Still another object is to produce metal inlays using either gravity or centrifugal casting processes.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a side view of the apparatus necessary to accomplish the present process using centrifugal methods.

FIG. 2 is a plan view of a portion of the device taken along line 22 of FIG. 1.

FIG. 3 is a plan view of a portion of the device taken along line 3-3 of FIG. 1.

FIG. 4 is a plan view of a portion of the device taken along line 4-4 of FIG. I.

FIG. 5 is a plan view of a portion of the wood surface showing the cavity for receiving the molten metal.

FIG. 6 is a cross section of a portion of the device taken substantially along line 6-6 of FIG. 2.

FIG. 7 is a cross section of a portion of the device taken substantially along line 7-7 of FIG. 4.

FIG. 8 is a cross section ,of a portion of the device taken along line 8.8 of FIG. 5.

FIG. 8A is the same cross section as FIG. 8 showing the cavity filled with metal.

FIG. 8B is the same cross section as FIG. 8 showing the wood and metal portion after sanding the surface of the metal and wood.

FIG. 9 is a side view of an alternative casting method using the process of the present invention with portions in cross section for purposes of clarity using gravity methods.

FIG. 10 is a cross section of still another alternative casting method using the described process.

FIG. 11 is a perspective view of a completed product illustrating a design which can be inlayed in wood.

FIG. 12 is a cross sectional view of a portion of the assembly showing another form of the invention.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION for making molds in which to cast metals using standard mold casting techniques. RTV is normally in a liquid state and by mixing the chemicals according to directions and then heating, it forms an elastic tough member which can withstand temperatures well in excess of 700F. Moreover, the mold. can be reused many times. The fact that RTV was originally used to cover the metal heat shields on the space agency vehicles to permit re-entry of the vehicles into Earths atmosphere attests to its great ability to withstand heat. Applicant has applied this modern space technology to the ancient art of inlaying metal in wood in a new and different manner with surprising results.

In the simplestform of the invention a coating of RTV material is placed on the outer surface of the wood to a thickness of about l/32 inch to 1/64 inch.

General Electric Corporations RTV designation No. 630 or No. 662 is satisfactory and is the same material used in the other described forms of the invention. RTV is basically a silicone rubber compound and is now manufactured by other firms. The desired thickness can be obtained by spreading the material with a spatula. The required thickness is dependent upon the temperature of the metal and the amount of metal that must flow past any particular point in the wood cavity. The RTV coating in addition to preventing physical contact between the molten metal and the wood surface also serves as a heat sump. In other words, as the molten metal flows into the cavities in the wood the RTV material rapidly absorbs heat from the molten metal thereby cooling it so that the intense initial heat will not have sufficient time to char the wood surface. The fact that this heat absorbing function operates in this manner in indicated by the fact that there is some charring of the wood in the undersides of the wood channel, but at the surface of the wood, there is no visible charring; indicating that the RTV material rapidly draws off the heat of the metal. Since one never sees the underside of the cavity in the wood unless the piece is actually destroyed this slight charring is not undesir able. Furthermore, this slight charring is so slight as to have no effect on the ability of the wood to tightly retain the metal inlay. After waiting 2 or 3 minutes, while the material levels itself, any air bubbles should be pricked with a pin. Using a low intensity flame from a small bunsen burner the material may be cured and solidified by passing the flame over the surface for about seconds.

In the case where the wood object to be inlaid is composed of soft wood or it has a thickness of less than inch, so that even a brief flame treatment to cure the silicone RTV coating might damage or warp the wood, a form of silicone RTV is obtainable that, when mixed with its proper catalyst, will, after being placed in its desired position self-cure itself in a relatively short time.

Next, a cavity is cut in the wood and in the RTV material to the desired depth. The cavity may be from about A; inch to inch in the wood to permit grinding conform to any artistic design required. When the cavity has been prepared, a metal having a pour tempera-.

ture of between 600 to 700F.-is selected; all of the metals belonging to the white metal group or alloys are satisfactory; such metals include tin, lead and sterling silver.

After the metal has solidified, the coating of RTV is removed and the wood and metal surface is sanded down until the desired smoothness has been attained. FIG. illustrates the above described process in which the wood number I is covered with a layer of RTV 2 and cavities 3 and 4 are formed in the wood as be routing. Small holes 7 are drilled in the base of the cavity at an angle of about 45 or less to secure the metal to the wood.

A procedure used to eliminate shrinkage cracks is employed in the above described process and is also used whether the method used is by gravity or centrifugal casting or whether various molds are used as will be described below. After the metal has solidified the wood and inlayed metal is at once subjected to a temperature of about 32F. In a cooling chamber to cause stress points or shrinkage cracks to occur so that such cracks will not occur in the hands of the consumer. After the cracking occurs, it is necessary to solder or weld all the visable cracks in the surface of the inlay. Where alloys of metals containing lead, antimony and tin or any combination thereof are used a soldering operation is required. Where the metal is pure tin, a sort of welding operation is used. The procedure is as follows: At each point where a crack occurs, a suitable quantity of RTV mixture is painted on the surface of the wood adjacent the crack in the inlay about A inch wide and about 1 inch long, at a thickness of about 1 /32 inch to 1/64 inch. Where any of the above mentioned alloys are used for filling the cracks, solder may be used without any appreciable difference in color hue from the surrounding metal. Where pure tin is used, only pure tin should be used in effecting the repair. The use of soldering flux should be held to a minimum, as it has a tendancy to leave a slight stain on the surface of the wood. A suggested flux is A muriatic acid, Vs glycerine, and /3 water. Tin does not require any flux.

To repair tin inlays, a strip of tin having about 4 to 5 times the bulk needed to fill the crack is placed upon the crack. A Wen soldering gun is used to melt the tin piece and the metal surrounding the crack. When melting has occurred, the soldering tip is removed and a small block of wood is used to gently press down the globule of molten metal. After the metal has congealed,

the block of wood is removed. Some metal will always spread to the RTV, but no damage will occur unless the metal is accidentally pushed onto the bare wood surface. After the repair has been effected, the excess metal is sanded down.

The preferred centrifugal casting method using the present method is shown in FIGS. l-7. The assembly is shown in FIG. 1 and the completed illustrative example is shown in FIG. 11. The assembly consists of the wood member 11 in which the design has been formed and shown as interconnected cavities 6. Note that small holes 7 are drilled in the bottom of the cavities at regular intervals to retain the metal.

The next step in the centrifugal method assembly or in the gravity method, is to form a pre-cured reusable RTV member 10 for overlaying the wood surface 12. It is essential that the RTV surface protective member fit the wood surface very tightly so that metal will not seep under the RTV surface and damage the wood. One method of preparing the surface protective memher is to use the wood member as a mold and pour liquid RTV on the surface of the wood, and using a containing frame, pour the protective member to a depth of about inch thick. If convenient, the protective member can be poured with a border which can be slipped over the wood member to further insure a perfect registration with the wood member. The RTV member is then cured by placing it in an oven at about 250F. and allowed to remain there for about one hour. After removing the RTV member from the oven, and cooling, the frame is removed and registration plugs may be cut in the RTV member for registration of the distribution member.

The distribution member or second member 13 is made from the same RTV material and is formed by placing a frame around the first RTV member and coating the top surface of the first member with a releasing agent such as a thin coating of vaseline. RTV material is then poured into the frame forming a distribution member about A inch thick.

Next, the protective member is removed from the wood member 11. The design 16 will now be perfectly molded in the surface 17 of the protective member. These protuberances are now removed as by cutting and only a shallow image 16 (a) as shown in FIG. 4!- is now cut into the surface 17. Passage ways 18 are drilled into member 10 in a cone shape so that after the metal is poured and solidified in the passageways, the protective member 10 may be separated from the wood member 11. The passageways should always be drilled so that they will open to the cavity 16 formed in the wood so that it will not touch the surface 12 of the wood.

The distribution member 13 is made in the following manner: An opening 21 is cut completely through the member at about the center in a slightly tapered manner. The opening may be about I A inch in diameter. This opening is to serve as a receiving cup through which the metal is poured.

V-shaped channels 22 are then cut in the lower surface 23 extending from the receiving cup 21 to the passageways 18 formed in the protective member 10. Each opening 18 has its own individual distribution V- channel 22.

AIR SUMPS It is to be noted that, as metal is poured into the receiving cup 21 and passes through channels 22, down through openings 18 and into the cavity 16 in the wood, it is scavenging the air in front of it and compressing it. Unless this air has some place to go, it will prevent metal from flowing into all of the areas of the cavity 16. Much of the air present in the cavities in the wood member is displaced by the incoming molten metal and is forced back up through the column of incoming metal, but at some points in the design small portions of air may become trapped thus producing points at which the metal will fail to completely fill out the design. To solve this problem, air sump reservoirs 26 are formed in surface 17 of member 10. The air reservoirs are connected to the cavity 16 by channels 27. Some metal will flow into said sump cavities which can then later be removed during sanding. Note that the channels should be opposite to the direction of the flow of the metal so that the metal does not fill the reservoir. Note also that the reservoirs are all placed radially inwardly of the cavity portions they connect so that as the assembly rotates, the centrifugal force will not fill the air reservoirs with metal. Thus if point 28 is the axis of rotation as shown in FIG. 4, all of the reservoirs are closer to the axis of rotation than the cavity with which they are immediately connected. Any metal which flows into the sumps may be removed from the design by sanding.

OPERATION OF THE CENTRIFUGAL CASTING METHOD After assemblying the members as shown in FIG. 1, the assembly is placed on a turn table of a motor driven centrifuge machine. Pressure plates 31 press tightly down on the assembly as the centrifuge turns. While the table is spinning, a suitable quantity of molten metal is poured into the center hole 32 in the pressure plate 33 and flows through opening 21 in the distribution member filling all of the grooves 22. The metal then flows down through openings 18 and into the design cavity 16. As described above, the air is purged to the air reservoirs 26. Metal continues to flow and to fill up the slight cavity 16a in the RTV member 10 which fills the wood cavity slightly above: the surface 12.

The metal is permitted to cool and then the centrifuge is stopped. The disassembly of the parts is as follows: First the pressure members 31 are released and the pressure plate 33 is removed. A pair of snips is placed between the flexible members 11 and 13 and the excess metal at the top of the passages 18 is cut ofi. The member 13 can now be lifted off and the excess metal in the feed system 22 removed.

Next, the member 10 is lifted from the wood member and the protruding metal is cut off. The last phase is to sand down the metal and wood until the desired smooth finish has been attained. The metal remains in the cavity of the wood and remains a part of the member 11.

After the sanding is completed, the member is placed in the cooling chamber for causing shrinkage cracks and the metal is finished by soldering as above described.

GRAVITY CASTING Still another form of casting that can utilize the principles of the above described invention is gravity casting. Referring to FIG. 9, a wood member 11a is placed on end. As before, the design is formed in the wood and indicated by cavities 16b. Small holes 7b are drilled at suitable intervals in the bottom of the cavity to lock the metal in place in the wood member. An RTV member 10a is formed in a manner similar to the method previ ously described and is placed against the wood surface. Passageways 18a connect the cavities 16b with a metal distribution member 41. The metal member is formed with a receiving cup 42 and passageways 43 formed in its surface which connect with the passageways 18a.

In operation, the metal is poured into the receiving cup, moves through the channels 43, through openings 18a and into the cavities 16b and holes 7b. The assembly is disassembled in the same manner as set forth above.

AIR EXHAUST SYSTEM As noted in the centrifugal system, the flowing molten metal compresses air in front of it and this air must be allowed to escape from the cavity in the wood. The most practical method is to provide an alternate system of air passages which parallel the metal passageways at the same elevations and lead to atmosphere. Since removal of air is a common casting problem and is somewhat empirical, it is not further described or shown on the drawing.

The above casting process, in addition to making complete objects, may be used to place a border for example around a coffee table. Instead of an extremely large RTV surface protector and RTV distribution system being used, the RTV members may be relatively small if the design is repeated around the border. Thus one section is cast at a time and then the assembly moved to the next section to be cast.

Still another form of the invention which utilizes the principles of the present invention is shown in FIG. 12. In this form of the invention, the objective is to imbed a precast metal design and surround it with molten metal to lock the design into the wood.

The process consists in preparing a precast metal design 51 which may be either flush with the wood surface or raised above. The precast member should have lugs 51a by which the molten metal will lock the design into the wood. The precast member is placed in the bottom of the cavity 53 which is formed with holes 54. A coating of RTV material 55 is then placed upon the wood surface of wood member 56. The exact proce dure is then followed as above described, in which metal is flowed into the cavity 53 and around the precast member 51.

It can be readily understood that the method shown in FIG. 9 can also be duplicated by the centrifugal casting process or the gravity process with minor modifica tions.

In summary, it should be noted that metal' casting is an art which requires much trial and error testing. It has been stated in this application that a plurality of passageways conduct the metal to the bare wood cavity forming the design. The number and spacing of these cavities can only be determined by a thorough knowledge of the art of casting. Obviously, there must be enough passageways so that the amount of metal and the time period that the metal is flowing at any point in the cavity is limited. Given enough metal flowing through a particular channel the wood will char. It is the invention of finding a material which can serve both as a conduit for the metal, a protective surface and as a heat sump that has made it possible to achieve a result never before achieved. It is both a mystery and an astounding achievement to be suddenly presented with a piece of wood with metal inlay design and to be told that the metal was actually poured directly into the wood. While the above description carefully describes the manner in which this result was achieved, the steps to achieve that object are truly unobvious to one skilled in the art.

The claims that follow set forth the essential steps of the invention.

I claim:

1. A process for inlaying molten metal in a prepared but uncoated wood surface cavity consisting of:

a. forming a cavity in the surface ofa wood member;

b. placing a quantity of RTV material outside said cavity and against the wood surface adjacent said cavity sufficient to prevent contact of molten metal with said wood surface and having sufficient thickness to rapidly absorb enough heat to prevent charring or burning of the surface of said wood, said RTV material being capable of withstanding temperatures well in excess of 700 F;

c. pouring molten metal having a pour temperature of approximately 700 F. or less into said cavity and permitting said metal to cool and solidify; and

d. sanding said wood and metal and wood surface until both are at the same elevation.

2. A process as described in claim 1 wherein said metal is a material selected from the white metals group.

3. A process as described in claim 1 consisting of:

a. subjecting said completed assembly to a temperature of about 32 F. to cause shrinkage cracks in said metal; and

b. filling said cracks with molten metal.

4. A process as described in claim 1 consisting of:

a. coating the surface of said Wood surface adjacent said cavity with RTV material in liquid form;

b. curing said RTV material until in a solid form; and

c. removing said RTV material in said step of sand- 5. A process as described in claim 1 consisting of:

a. preparing a cured reusable RTV member for overlaying said cavity;

b. forming a plurality of openings in said cured RTV member for pouring metal therethrough, said openings being formed for registration with said cavity;

c. placing said RTV member in registration with said surface of said wood member for excluding metal from entering between said matched surfaces and covering said cavity; and

d. removing said RTV member after said metal solidifies.

6. A process as described in claim 5 consisting of:

a. preparing a second reusable RTV member having a bottom surface formed for close fitting registration with the top surface of said first RTV member, and said lower surface of said second member being formed with grooves forming a passage for said metal from said opening in said second RTV member to said openings in said first RTV member.

7. A process as described in claim 6 consisting of:

a. means clamping said assembly of said wood member, and said first and second RTV members together; and

b. rotating said assembly during the pouring of said molten metal into said cavity.

8. A process as described in claim 6 consisting of:

a. forming a mirror image depression in the bottom surface of said first RTV member permitting an excess of metal to form above said cavity.

9. A process as described in claim 8 consisting of:

a. forming air sump reservoirs in said first RTV member by forming a depression in the bottom surface of said first RTV member and a channel communicating between said air sump reservoirs and said cavity in said wood; and

b. permitting said compressed and displaced air from said cavity in said wood member to enter said air sump reservoirs.

10. A process as described in claim 5 consisting of:

a. placing a metal member in close fitting registration against the RTV surface opposite to that surface in contact with said wood member; said metal member being formed with a cup shaped reservoir formed as a cavity in the surface in contact with said RTV member and channels formed in said metal member connecting said cup shaped reservoir and said openings in said RTV member.

11. A process as described in claim 1 consisting of the steps of:

a. preparing a precast metal design;

b. placing said precast metal design within said cavity so that portions of said precast design will be visible after said molten metal is inserted into said cavity; and

c. placing said precast design in said cavity so that it will be surrounded and affixed to said wood member by said molten metal. 

1. A process for inlaying molten metal in a prepared but uncoated wood surface cavity consisting of: a. forming a cavity in the surface of a wood member; b. placing a quantity of RTV material outside said cavity and against the wood surface adjacent said cavity sufficient to prevent contact of molten metal with said wood surface and having sufficient thickness to rapidly absorb enough heat to prevent charring or burning of the surface of said wOod, said RTV material being capable of withstanding temperatures well in excess of 700* F; c. pouring molten metal having a pour temperature of approximately 700* F. or less into said cavity and permitting said metal to cool and solidify; and d. sanding said wood and metal and wood surface until both are at the same elevation.
 2. A process as described in claim 1 wherein said metal is a material selected from the white metals group.
 3. A process as described in claim 1 consisting of: a. subjecting said completed assembly to a temperature of about 32* F. to cause shrinkage cracks in said metal; and b. filling said cracks with molten metal.
 4. A process as described in claim 1 consisting of: a. coating the surface of said wood surface adjacent said cavity with RTV material in liquid form; b. curing said RTV material until in a solid form; and c. removing said RTV material in said step of sanding.
 5. A process as described in claim 1 consisting of: a. preparing a cured reusable RTV member for overlaying said cavity; b. forming a plurality of openings in said cured RTV member for pouring metal therethrough, said openings being formed for registration with said cavity; c. placing said RTV member in registration with said surface of said wood member for excluding metal from entering between said matched surfaces and covering said cavity; and d. removing said RTV member after said metal solidifies.
 6. A process as described in claim 5 consisting of: a. preparing a second reusable RTV member having a bottom surface formed for close fitting registration with the top surface of said first RTV member, and said lower surface of said second member being formed with grooves forming a passage for said metal from said opening in said second RTV member to said openings in said first RTV member.
 7. A process as described in claim 6 consisting of: a. means clamping said assembly of said wood member, and said first and second RTV members together; and b. rotating said assembly during the pouring of said molten metal into said cavity.
 8. A process as described in claim 6 consisting of: a. forming a mirror image depression in the bottom surface of said first RTV member permitting an excess of metal to form above said cavity.
 9. A process as described in claim 8 consisting of: a. forming air sump reservoirs in said first RTV member by forming a depression in the bottom surface of said first RTV member and a channel communicating between said air sump reservoirs and said cavity in said wood; and b. permitting said compressed and displaced air from said cavity in said wood member to enter said air sump reservoirs.
 10. A process as described in claim 5 consisting of: a. placing a metal member in close fitting registration against the RTV surface opposite to that surface in contact with said wood member; said metal member being formed with a cup shaped reservoir formed as a cavity in the surface in contact with said RTV member and channels formed in said metal member connecting said cup shaped reservoir and said openings in said RTV member.
 11. A process as described in claim 1 consisting of the steps of: a. preparing a precast metal design; b. placing said precast metal design within said cavity so that portions of said precast design will be visible after said molten metal is inserted into said cavity; and c. placing said precast design in said cavity so that it will be surrounded and affixed to said wood member by said molten metal. 